1. Field of the Invention
The invention relates to a system for steering a missile by means of lateral gas jets and a missile comprising such a system.
When a missile is to be steered with high load factors, lateral nozzles are provided on board this missile which are fed with gas either from a gas generator of the main thrustor, or from a gas generator specially provided for this purpose. Thus, lateral gas jets are provided generating transverse propulsive forces capable of rapidly and appreciably changing the direction of the trajectory of the missile. The action lines of such transverse forces can be caused to pass through the center of gravity of the missile, or at least in the vicinity thereof and then the missile is said to be force steered, the response time to the control being then particularly fast. However, this is not obligatory and the lines of action of said transverse forces may pass through points of the axis of the missile different from the center of gravity. Said transverse forces then create, similarly to conventional aerodynamic steering surfaces, moments for controlling the missile in attitude with respect to the center of gravity.
2. Description of the Prior Art
From the U.S. Pat. No. 4,531,693 and the U.S. Pat. No. FR-A-2 620 812, a system is known for steering a missile by means of lateral gas jets, comprising a gas generator able to be connected to at least a pair of lateral nozzles via rotary valving members, moving under the action of the drive means and controlling the passage of the gases through said nozzles.
In the system of the American patent U.S. Pat. No. 4,531,693, with each of said nozzles there is associated an individual rotary valving member, itself being controlled individually by an oscillator. With this structure, each rotary valving member may have low inertia so that the response time of the valving means and so of the steering may be very small.
Furthermore, because there is an oscillator for each of said valving members, it is easy to control the whole of said oscillators so that, at all times, the position of each valving member (completely open, total closure or partial closure) corresponds exactly to the steering phase and/or to the state of said gas generator. On the other hand, because said rotary valving means are controlled by oscillators, a controlled position of a valving member with respect to the corresponding nozzle is not reached directly, but by a train of oscillations. In addition, these oscillations may induce parasite oscillations in the missile, complicating steering thereof.
On the other hand, in the system of the French patent FR-A-2 620 812, to provide the necessary control coupling between said nozzles, a rotary valving means is provided common to the two nozzles, this valving means being controlled by the piston of a jack whose two chambers, having different cross sections, receive a part of the gas generated by said generator, the position of the piston of said jack, and so that of said valving means, being controlled by controlling the flowrate of said gas in that one of said chambers of the jack which has the largest cross section. With such a control, the rotary valving means may reach its position directly, without oscillations. However, in this case, the rotary valving means is necessarily cumbersome, so that its inertia and its response time are high.